Stud manipulating device

ABSTRACT

A device for inserting and removing studs 16 from bores 19 in a workpiece, for example a nuclear reactor vessel, comprises manipulating devices 22 for operating on individual studs. Each device 22 is capable of tensioning a stud 16, slackening a working nut 17 on the stud, and subsequently removing the stud from the bore. A ring 92 has dogs 93 which can engage recesses in the working nut to interlock with the nut against relative rotation. Motors 100 are coupled to the ring 92 and operable to rotate the working nut. A top nut 51 is coupled to motor 100 which are operable to rotate the nut and screw it onto the stud 16. The top nut 51 together with other operating parts of the device can be raised and lowered on a tube 61 by means of a hydraulic actuator 65. A hydraulic load cell 52 is located between the top nut and a stool 53 which rests on the workpiece. The load cell 52 can be pressurized to tension the stud 16 by means of the top nut 51 and thus facilitate rotation of the working nut 17 when tightening or slackening. A dog clutch mechanism 26 provides means for engaging an end fitting 25 on the stud and locking it against relative axial and rotational movement. The dog clutch mechanism can be raised and lowered on a guide member 36 by an actuator 38. The dog clutch mechanism has a tubular member 42 and the drive coupling for the motor 100 to the top nut 51 includes a tubular member 61. Both of the tubular members 42 and 61 carry teeth 43 and 85 which are engagable with one another to provide a clutch. The teeth 43 and 85 are engaged when the top nut 51 is raised and the dog clutch mechanism 26 is lowered, to provide a coupling between the motors 100 and the dog clutch mechanism for rotating the stud.

The present invention is concerned with a device for use in inserting,tensioning and removing screw-threaded studs. It is concernedparticularly for use in inserting and removing the studs which holdtogether atomic pressure vessels but other applications of the deviceare possible.

In an atomic pressure vessel the cover is usually held in place by meansof closely spaced screw-threaded studs which are inserted intoscrew-threaded bores in a flange around the top of the body of theatomic pressure vessel. The studs pass through bores in the periphery ofthe cover which is placed over the body and the cover is clamped inplace by tightening working nuts onto the exposed ends of the studs. Inthe past the studs and nuts have been inserted and removed with the aidof hand held power tools by workmen working directly on top of thecover. Each stud is inserted and each nut tightened individually.Because of the level of radiation at the cover and the time needed tofit all the stud and nuts each workman may be exposed to the full yearlydose of radiation which regulations permit, during one operation.

More recently multiple stud tensioning devices have been designed whichcan operate on several studs simultaneously, tensioning the studs andtightening or slackening the working nut as required. Separate multiplestud removing devices have also been designed which, once the workingnuts have been removed can remove several studs from their respectivescrew-threaded bores simultaneously.

The present invention provides a device which can insert a stud into abore, tension the studs, tighten a working nut on the stud, slacken theworking nut on the stud and remove the stud from the bore. In itspreferred form the invention provides several such devices which can beoperated simultaneously.

According to the present invention there is provided a stud manipulatingdevice for inserting a stud into a bore in a workpiece, tensioning thestud, tightening a working nut on the stud, or for slackening the nut onthe stud and removing the stud from the workpiece, the device comprisingmeans for engaging the working nut and interlocking with the nut againstrelative rotational movement, first drive means coupled to the workingnut engaging means and operable in use to rotate the working nut, a topnut for securing onto the end of the stud, second drive means operableto rotate the top nut, means for raising and lowering the top nut, ahydraulic pressure member located between the top nut and the workpieceand operable to tension the stud by means of the top nut, stud engagingmeans engagable with the stud to interlock with the stud againstrelative rotational movement, means for raising and lowering thestud-engaging means, and clutch means operable between the second drivemeans and the stud engaging means and which is engaged when the top nutis in a raised position and the stud-engaging means is in a loweredposition, to couple the stud engaging means in rotation with the seconddrive means.

To remove a stud using this device the stud engaging means is engagedwith the end of the stud. The stud may have a specially formed end partfor interlocking with the stud engaging means. The top nut is lowered tothe stud and rotated by the second drive means to screw it on the end ofthe stud. The hydraulic pressure member is pressurised to raise the topnut and thus tension the stud. With the stud tensioned the working nutis unscrewed using the first drive means. The tension in the stud isreleased by releasing the pressure in the hydraulic pressure member andthe top nut is unscrewed from the stud and raised until the clutch meansengage. The second drive means are then operated to unscrew the studfrom its bore.

To insert a stud, tension it and tighten the working nut the operationis performed in reverse.

In the preferred form of the invention several such devices are providedand their drive means and raising and lowering means interconnected foroperation in unison.

We have also invented a method of preventing water entering the boresfor the studs when the reactor vessel is flooded following removal ofthe stud.

The invention also provides a method for preventing water entering boresin a nuclear reactor vessel when studs are removed from the vessel andthe vessel is flooded with water comprising filling the bores with aquiescent non-corrosive liquid that is immiscible with water and has aspecific gravity greater than water, to a level just below the tops ofthe bores.

An embodiment of the invention will now be described by way of examplewith reference to the accompanying drawings of which:

FIG. 1 shows a perspective view of a multiple stud fastening, tensioningand unfastening device according to the invention above an atomicreactor vessel;

FIG. 2 shows a view similar to FIG. 1 but with the device lowered ontothe vessel;

FIG. 3 shows a view similar to FIGS. 1 and 2 but with the cover of thereactor vessel being lifted clear of the vessel;

FIG. 4 shows an enlarged elevation of two manipulating devices of thedevice of FIGS. 1 to 3.

FIG. 5 is a view, partly in section on an enlarged scale of astud-engaging means of a manipulating device as shown in FIG. 4, in thelocking position;

FIG. 6 is a view similar to FIG. 5 but with the parts shown duringunlocking;

FIG. 7 shows a perspective view of a stud end fitting of the engagingmeans of FIGS. 5 and 6;

FIG. 8 shows a perspective view of a key member of the engaging means ofFIGS. 5 and 6;

FIG. 9 shows a perspective view from below of a tubular member of thestud-engaging means of FIGS. 5 and 6;

FIG. 10 shows in elevation an actuator of the means for raising andlowering the stud-engaging means of FIGS. 5 and 6;

FIG. 11 shows an enlarged elevation, partly in section of the actuatorof FIG. 10;

FIG. 12 shows on an enlarged scale in vertical section, the lower partof the manipulating device of FIG. 4;

FIG. 13 shows in plan view on an enlarged scale the hydraulic pressuremember of the manipulating device of FIG. 4;

FIG. 14 shows a vertical section through the hydraulic pressure memberof FIG. 13;

FIG. 15 shows in vertical section the telescopic guide tube and meansfor raising and lowering the lower part of the manipulating device ofFIG. 4;

FIG. 16 shows in vertical section the top nut of the manipulating deviceof FIG. 4;

FIG. 17 shows in vertical section the working nut engaging means;

FIG. 18 shows in plan view the lower part of the manipulator of FIG. 4with parts of the drive means for the top nut and the working nut;

FIG. 19 shows in vertical section a stool of the lower part shown inFIG. 12;

FIG. 20 shows, partly in section, an elevation of the drive motors ofthe manipulating device of FIG. 4; and

FIG. 21 shows in plan view the drive motors of the manipulating deviceof FIG. 4.

Referring to FIGS. 1 to 3, these show a multiple stud fastening,tensioning and unfastening device 11 mounted above an atomic reactorpressure vessel 12. The three figures show the device at differentstages in the operation of unfastening the studs.

The atomic reactor pressure vessel includes a cover 13 which is securedto a flange 14 around the top of the body of the pressure vessel bymeans of sixty screw-threaded studs 16 and nuts 17. The studs passthrough closely spaced holes 18 in the periphery of the cover and engagescrew-threaded bores 19 (see FIG. 4) in the flange 14. The nuts 17 aretightened on the studs to clamp the cover 13 against the flange 14.Pairs of spherical washers 20 are placed under the nut 17.

The device 11 comprises an annular working platform 21 mounted over thereactor vessel and carrying thirty individual nut manipulating devices22. The working platform together with the thirty manipulating devicescan be lowered onto three locating dowel pins (not shown) on the reactorvessel.

The devices 22 are movable in unison on a horizontal circumferentialrail 23 mounted below the platform 24 between positions set by stops(not shown). When the manipulating devices are set against the clockwisestops they are positioned above one set of alternate studs 16 and whenthey are set against the anticlockwise stops they are positioned overthe other set of alternate studs. In this way the manipulating devicescan be used for simultaneously operating on half the studs and thenmoved and used to operate on the other half of the studs. It will beappreciated that arrangements in which other sub-multiples of the numberof studs are used for the number of manipulating devices are possible,the corresponding fraction of the studs being operated upon eachposition.

FIG. 1 shows the devices in position prior to being lowered onto one setof studs and nuts. FIG. 2 shows the devices during slackening the nutsand unfastening the studs of one set and FIG. 3 shows the cover beinglifted clear of the flange with all the studs and nuts supported onlongitudinally split hinged collars 24.

FIG. 4 shows two of the manipulating devices in greater detail. For thepurposes of illustration one is viewed from a position at right anglesto the other and one is shown in a retracted condition whereas the otheris in the extended position. It will be appreciated that in practice themanipulating devices have the same orientation relative to the adjacentpart of the platform and that they move in unison so that all areextended and retracted together.

As can be seen in FIG. 4 the upper end of the stud is provided with afitting 25. This fitting co-operates with a stud-engaging part of themanipulating device to form a dog clutch mechanism 26 which, whenengaged, inter-locks the stud engaging parts of the manipulating deviceand the stud against relative axial and the rotational movement. Thestud-engaging part and the stud are shown in FIGS. 5, 6, 7, 8 and 9 ofwhich FIGS. 5 and 6 show them in the locked and unlocked conditionrespectively. FIG. 7 shows the stud fitting and FIGS. 8 and 9 show theother parts of the clutch mechanism.

The fitting 25 at the upper end of the stud may be a separate fittingsecured to the stud by a cross pin 27 as shown in the drawings orotherwise, or it may be an integral fitting machined onto the top of thestud. It comprises a splined head 28 of cross-shaped transverse crosssection with an undercut 29 below the head. The fitting thus providedfour equally circumferentially spaced radially-outwardly projecting lugs30 with downwardly sloping upper surfaces and radial lower surfaces. Theundercut 29 provides an annular space below the lugs 30.

The parts of the manipulator device which comprise the stud-engagingparts or dog clutch are a tubular claw coupling member 31 and a lockingplate or key member 32. The claw coupling member comprises an annularwall with four equally circumferentially spaced radially inwardlyprojecting lugs 33. The spaces between the lugs 33 are large enough toreceive the lugs 30 of the fitting 25 on the stud. The axial thicknessof the lugs 33 is less than the axial length of the annular clearancespace below the lugs 30 provided by the undercut 29 so that after thelugs 33 and 30 have been slid past each other the lugs 33 can be broughtbehind the lugs 30 by turning the claw coupling member 31 through 45° inthe manner of a bayonet fitting. The claw coupling member and thefitting 25 can then be locked in this position by lowering the lockingplate or key member 32.

The locking plate 32 comprises a base 34 from which four axiallyextending fingers or lugs 35 project downwardly. The fingers 35 fit intothe axially aligned spaced between the lugs 33 and the lugs 30 so as tokey the claw-coupling member to the fitting 25.

As shown in FIGS. 7 and 9, four pins 111 are provided on the upper sideof the stud fitting 25 and four complementary arcuate slots 110 areprovided in the underside of the claw coupling member 31. The slots eachsubtend an angle of about 45° at the axis of the tubular claw couplingmember. The pins 111 engage the slots 110 when the claw coupling memberis lowered into position on the stud so as to limit the relativerotational movement of the claw coupling member on the one hand at thepoints at which the spaces between lugs 30 and the spaces between lugs31 are axially aligned and on the other hand at the point at which thelugs 31 are aligned with the spaces between the lugs 30. In this wayengagement of the locking plate and disengagement of the claw couplingmember from the stud are facilitated.

The locking plate 32 is carried at the lower end of a guide tube 36extending centrally down the manipulating device. The upper end of thetube 36 is secured to a cross-head plate 37 (see FIG. 4) which ismovable vertically by means of two hydraulic actuators 38 connectedbetween the cross-head plate and the top plate 39 of the manipulatingdevice.

The locking plate is coupled to the claw coupling member 31 by an axiallost-motion coupling formed by axial slots 40 in the fingers of thelocking plate 32 which receive pins 41 fixed in the upper part of theannular wall of the tubular claw coupling member. The movement of thepins 41 up the slots 40 allows limited relative axial movement of theclaw coupling member and the locking plate.

When the actuators 38 are retracted the cross-head plate, the guidetube, the locking plate and the claw coupling member are lowered ontothe fitting 25. The lugs 33 pass down through the spaces between thelugs 30. The claw coupling is rotated through 45° to bring the lugs 33beneath the lugs 30 while the locking plate 32 still remains above theend fitting, the pins 41 being at the lower ends of the slots 40. Thelocking plate is then lowered to bring the fingers 35 between the lugs33 and 30 keeping them together as the pins 41 move up the slots 40.

As can be seen in FIG. 9 a cylindrical drive tube 42 is secured to thetop of the claw coupling 31 and this tube carries at its upper end,around its outside, gear teeth 43. The gear teeth 43 and the drive tube42 form part of the stud rotating mechanism that will be describedbelow.

FIG. 10 shows details of the top plate 39 and the actuators for thestud-engaging parts whilst FIG. 11 shows the actuators in greaterdetail.

The actuators 38 are fitted in holes 44 in the top plate and comprisepistons 45 with piston rods 46 secured to the cross-head plate 37. Thepistons move in cylinders 47 which are supplied with hydraulic fluidthrough hydraulic pipe couplings 48. When the pressure in the cylindersis low the pistons descend under the weight of the cross-head block 37and the parts carried by the cross-head block. When the actuators arepressurised hydraulic fluid flows through the pipe coupling 48, down thespace between the cylinders 47 and an outer sleeve 49 in grooves 50provided for this purpose and into the spaces below the pistons 50. Thepressure raises the pistons 45 and with them the cross-head piece andthe stud engaging parts.

Referring now to FIG. 4, and 12 the manipulating device includes a topnut 51 which can be screwed onto the end of the stud, and a hydraulicpressure member or load cell 52 of the type described in our PatentApplication No. 4284/77 (German OLS No. 2804313.2) which is locatedbetween the top nut and a skirt or stool 53 which can be lowered aroundthe working nut 17 to rest on the cover 13. These parts are all shown ingreater detail in FIG. 12 and the hydraulic load cell is shown in FIGS.13 and 14. The hydraulic load cell differs from that shown in FIGS. 1and 2 of the abovementioned application principally in that arcuaterecesses 54 are provided in the sides of the body to provide clearancefor the adjacent studs and their nuts with the load cell 55 beingmodified accordingly. With the top nut screwed down against the uppersurface 56 of the load cell 52, the load cell can be pressured withhydraulic fluid through a filling bore 57 so that the annular piston 58is forced out of the groove 59 against the top of the stool 53 thustensioning the stud and allowing the working nut 17 to be turned.

Referring now to FIG. 15 which shows the upper part of the manipulatingdevice in greater detail, two cylindrical tubes 60 and 61 are fittedtogether in a telescopic manner. The upper end of the upper tube 60 isfixed to the top plate 39. The lower tube 61 fits inside the tube 60 andis free to slide up and down and to rotate inside the tube 60.

A thrust bearing 62 couples the upper end of the lower tube 61 to acylinder 63 which together with an annular piston 64 forms the movablemember of a hydraulic actuator 65. The piston 64 carried by the cylinder63 forms a sliding seal against a tube 66. The lower end of the space 67between the cylinders 63 an the tube 66 is closed by sliding seals 68carried by the inner tube 66 and an end sliding seal 69 is provided onthe cylinder 63 and bears against the tube 66. The cylinder 66 is fixedto the top plate and accommodates the guide tube 36.

The space 67 is connected to a source of hydraulic fluid by means ofconduits contained within the annular space between tube 66 and guidetube 36. These conduits emerge as 112 and 113. Pressure applied at 112will retract the actuator into the position shown in the drawing.Bleeding off pressure at 112 will allow the actuator to lower under theweight of the stool 53 the top nut 51 and the load cell 52.Alternatively the actuator can be powered into the fully extendedposition by pressurizing at 112.

Referring again to FIG. 12, this shows that the lower end of the tube 61is attached to an outwardly-turned flange 70 which carries a circle ofdownwardly-projecting rubber-covered pegs 71. The pegs 71 are receivedin a ring of matching bores 72 in the upper surface of the top nut ascan be seen more clearly in FIG. 16. The pegs and the bores provide atorque transmitting coupling between the tube 61 and the top nut 51.

The assembly of the tube 61 and the top nut 51 is free to rotaterelative to the tube 60 and the lower part of the manipulating device.The drive means for rotating the top nut will be described below.

The lower end of the manipulator includes a base plate 80 which isfastened by bolts 81 and spacers 82 to the skirt 53. The base plate hasa central hole through which the tube 61 passes with clearance. Anannular rebate around the lower edge of the central hole accommodatesthe flange 70 of the tube 61. A thrust bearing surface 83 is providedbetween the flange 70 and the overhanging part around the edge of thehole. Gear teeth 84 are provided on the outside of the tube 61 above thebase plate 80 for meshing with a pair of pinions 102 on the top of thebase plate 80. The pinions 102 serve for rotating the tube 61 and inturn rotating the top nut 51.

On the inside of the tube 61 are a second set of gear teeth 85. When thetube 61 and the drive tube 42 are in the relative positions shown inFIG. 12 the teeth 85 engage the teeth 43 to provide a splined couplingbetween the tube 61 and the tube 42. This occurs when the tube 61 is ina raised position and the tube 42 is in a lowered position. Thus whenthe tube 61 is raised rotation of the tube 61 not only rotates the topnut but also the claw coupling member and thus, when engaged with theend fitting 25, the stud 16.

Lowering of the tube 61 causes the teeth 85 and 43 to become disengagedand in this condition rotation of the tube 61 rotates only the nut 51.

The upper end of the working nut 17 is provided with a series ofregularly-spaced rectangular recesses 90 (see FIG. 12) which gives thenut a castellated appearance. Carried inside the skirt 53 on bearing 91is a working nut engaging a ring 92 with dogs 93 that are engageable inthe recesses 90 in the working nut 17. The bearings 91 permit ring torotate relative to the skirt and at the same time are designed to retainthe ring 92 in position on the skirt. FIG. 17 shows the ring in greaterdetail. Around the outside of the ring 92, gear teeth 94 are provided.These teeth mesh with two pinions 95 located in slots 96 in the side ofthe skirt (see FIGS. 18 and 19). Rotation of the pinions 95 causes thering 92 to rotate and thus, when the dogs 93 are engaged with therecesses 90 in the lower nut 17, causes the lower nut to rotate.

For rotating the top and working nuts four hydraulic motors 100 aremounted on the top plate 39 around the central opening that is providedfor the guide tube 36. FIGS. 20 and 21 show these motors. The driveshafts from the motors pass through holes in the top plate end arecoupled to respective telescopic drive shafts 101. Each drive shaftcomprises a square-section tube 114 as the upper part and a squaresection rod 115 as the lower part which is a sliding fit in the upperpart.

At their lower ends one diagonally opposite pair of drive shafts isfixed to the pair of pinions 102 (see FIGS. 12 and 18) mounted forrotation on top of the base plate 80 and meshing with the gear teeth onthe outside of the tube 61 for turning the top nut 51 and, selectively,the stud 16.

The other diagonally opposite pair of shafts 101 are fixed to pinions103 mounted for rotation on top of the base plate 80 which mesh with agear train terminating in the pinions 95 which turn the ring 92 and thusthe lower nut 17. The gear train comprises gears 104 and 105 on top ofthe base plate, drive shafts 106 on which gears 105 and gears 107 arefixed and meshing gears 107, 108 and 95 mounted in the slots 96 in theskirt.

The procedure for removing studs is as follows. The working platform 21is lowered onto the locating dowels on the service structure. The powermains (115 volts a.c. single phase) and high and low pressure links(high for the load cell and low for the other hydraulics) are connectedto the electrical and hydraulic ring mains on the working platform. Thecontrols for these supplies are situated in a control station remotefrom the reactor vessel. The low pressure hydraulic supply is raised to500 p.s.i. which causes the actuator 65 to raise the tube 61 and theactuator 38 to raise the guide tube 36 so that all the stud manipulatingdevices are in the retracted condition. These are then set aginat theclockwise stops to position them over one set of alternate studs.

The first operation is to release the pressure in the actuator 38allowing the guide tube 36 and stud engaging parts to descend undertheir own weight. The lugs 33 of the claw coupling member will passbetween the lugs 30 and the gear teeth 85 on the drive tube 42 will beat the same time lowered into a position in which they mesh with theteeth 43 and so energisation of the motors at low pressure causes themto rotate just enough for the lugs 33 to enter below the lugs 30 and thelocking plate 32 to drop into place keying the two parts together. Thepressure is not sufficient to turn the stud once the clutch mechanism isengaged. A disc indicator 120 attached to the top of the guide tube 36provides a visual indication to the operator from a distance confirmingthat locking has been achieved by producing no visual indication whenthe stud rotating mechanism is operated at low pressures in bothdirections.

The pressure in the actuator 65 is then reduced to 120 p.s.i. allowingthe tube 61 to descend slowly. 95% of the weight of the nut andmanipulator parts carried by the tube 61 is borne by the 120 p.s.i.pressure. The top nut is guided by the drive tube 42 onto the top end ofthe stud 16. The gear teeth 43 and 85 disengage as the tube 61 descends.

Each top nut drive mechanism is then energised by energising theappropriate pair of hydraulic motors at low pressure to rotate throughthe pinions 102, the tube 61 and hence the nut 51 at low speed, say 20r.p.m. Self aligning of the threads of the nut and the stud should occurin a matter of two or three seconds. When all studs are engaged therotator speed is automatically raised to 100 r.p.m., on all manipulatorsso that the top nuts 51 are screwed down into engagement with the loadcells 52 in about a minute. When all the nuts are home the motors areautomatically reversed to screw back each top nut by one commplete turn.The load cells are then pressurised to the original tightening pressureof the stud. The working nut drive mechanisms are then operated tounscrew all working nuts 17 one turn. This is effected by energising theappropriate pairs of hydraulic motors 100 which, operating through thepinions 103, 104 and 105, drive shafts 106 and pinions 107, 108 and 109turn the rings 92 which, engages by their dogs 93 the working nuts 17.

This achieved, the load cell pressure is released and the tension on thenut will have been reduced sufficiently for the studs to be turned bythe stud rotator mechanism. Firstly however with the pressure in theactuator 65 maintained at 120 p.s.i. the top nuts are unscrewed. Theactuator 65 is then pressurised to 500 p.s.i. to raise the tube 61 sothat the teeth 85 engage the teeth 45 on the outside of the tube 42.With these teeth engaged rotation of the top nut rotating mechanism alsorotates the drive tube and hence the claw coupling mechanism. Theactuators 65 draw up the studs as they are unscrewed some 8" into thecover 13 to clear the flange 14.

The hinged split sleeves 24 are lowered by hand using light tubularmanipulators (not shown) to close around the 8" length of exposed studbetween the underside of the nut 17 and the spherical washers. Theactuators are lowered so that the weight of the lower nut and stud aretaken by the split sleeve.

The stud engaging parts are then freed from the stud by raising theguide tube 36 while rotating the claw coupling. The stud manipulatorsare raised a further 3" to be clear of the stud ends.

All manipulators are then swung against the anticlockwise stops and theoperation is repeated on the other set of studs.

The top cover 13 can be lifted off the flange 14 by means of lugs 130.

The top cover is lifted complete with the following parts:

All 50% tensioners remain secured to their studs resting on their safetysleeves, and ready for the final reassembly.

The The first batch of 50% studs remain resting on their safety sleeves.

The self aligning washers remain in place on the cover.

The weight of all the additional equipment for a 60 stud installationamounts typically to:

    ______________________________________                                        30 MSTs complete with manipu-                                                                    = 30 × 750 lbs                                                                      ≃ 10.0 tons                      lators                                                                        60 studs, lower nuts, and washers                                                                = 60 × 700 lbs                                                                      ≃ 19.0 tons                      Walkway working platform       ≃ 10.0 tons                                                     ≃ 39.0 tons                      ______________________________________                                    

Alternatively the working platform complete with the above equipment(except washers) may be transported to the parking bay using theexisting spreader suspended from the crane hook.

After the cover has been removed the reactor and surroundings areusually flooded to a level of say 25 feet while the spent core isremoved and replaced. To prevent water entering the stud holes andcausing corrosion the present practice is to fit plates over theindividual stud holes by hand. The water is drained down and the coversare removed before the studs are refitted. To eliminate this timeconsuming practice the stud holes may be flooded to a depth say 1/4"below the surface of this joint with a non-corrosive liquid. A highgravity quiescent water repellent fluid is suitable for this purpose.The fluid is injected into the bores through a manifold 117 (see FIG. 4)and connecting branches drilled in the flange 14. Overflow branches andmanifold (not shown) are provided 1/4" below the top of the bore toprevent the fluid overflowing the bore. Complete draining of this fluidthrough the manifold 117 will be provided before the studs are screwedin. The fluid leaves the bores clean, lubricated and prevents corrosion.The manifold may be formed in three sections, each serving 20 bores toprevent too large a pressure variation in the fluid delivered todifferent bores.

I claim:
 1. A stud manipulating device for inserting a stud into a borein a workpiece, tensioning the stud, tightening a working nut on thestud, or for slackening the nut on the stud and removing the stud fromthe workpiece, the device comprising means for engaging the working nutand interlocking with the nut against relative rotational movement,first drive means coupled to the working-nut engaging means and operablein use to rotate the working nut, a top nut for securing onto the end ofthe stud, second drive means operable to rotate the top nut, means forraising and lowering the top nut, a hydraulic pressure member locatedbetween the top nut and the workpiece and operable to tension the studby means of the top nut, stud engaging means engagable with the stud tointerlock with the stud against relative rotational movement, means forraising and lowering the stud-engaging means, and clutch means operablebetween the second drive means and the stud engaging means and which isengaged when the top nut is in a raised position and the stud-engagingmeans is in a lowered position, to couple the stud engaging means inrotation with the second drive means.
 2. A device according to claim 2in which the stud engaging means is adapted to engage an upper endportion on the stud which has circumferentially-spaced radiallyoutwardly projecting lugs with an annular space beneath them, and thestud engaging means comprises a tubular member withcircumferentially-spaced radially inwardly projecting lugs which canpass between the radially outwardly projecting lugs on the end portionof the stud and can be rotated in the annular space into a lockingposition in which they are located below the outwardly projecting lugs,and a key member with circumferentially-spaced axially downwardlyprojecting lugs which can enter the aligned spaces between the radiallyoutwardly projecting lugs and the radially inwardly projecting lugs whenthe lugs are in the locking position, to lock the tubular member to theend portion of the stud against relative axial and rotational movement.3. A device according to claim 2 in which the key member is fixed to thetubular member so as to permit limited relative axial movement, theaxially projecting lugs being aligned with the spaces between theradially inwardly projecting lugs.
 4. A device according to claim 1 inwhich the stud-engaging means serves as a guide for lowering the toponto the stud.
 5. A device according to claim 1 in which the studengaging means includes a tubular member and the second drive meansincludes a tubular member coaxial with the tubularly member of the studengaging means and the clutch means comprises a ring of radial inwardlyprojecting teeth and a ring radially outwardly projecting teeth onrespective ones of the tubular members and which can be brought intoengagement by relative axial movement of the tubular members, so as toprovide a splined connection between the tubular members.
 6. A deviceaccording to claim 1 comprising an upper part which carries motors ofthe first and second drive means and actuators for the raising andlowering means and a lower part which carries the top nut, the pressuremember the clutch means and the stud engaging means, and the working nutengaging means, the motors being connected to the working nut engagingmeans and the top nut by splined telescopic drive shafts and the lowerpart being connected to the upper part by telescopic guide tubes.